JPH10325021A - Titania fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a titania fiber having specific physical properties and useful for catalyst supports for reduction of nitrogen oxide, photocatalyst, filters, etc., for high temperature by subjecting a titanium alkoxide solution to hydrolysis and polymerization reaction, dissolving the resultant polymer into an organic solvent to form a spinning solution and carrying out spinning and baking. SOLUTION: Water is added to an alcohol solution of titanium alkoxide and hydrolysis reaction and polymerization reaction are carried out to produce and deposit a polymer insoluble in the alcohol. Then, the polymer is dissolved in an organic solvent to afford a spinning solution and the spinning solution is spun to afford a precursor fiber and the precursor fiber is baked to provide the objective fiber having 5-50 μm fiber diameter, >=50 cm fiber length, >=0.5 GPa tensile strength of single fiber by titanium alkoxide method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a titania fiber which can be used as a catalyst carrier for reducing nitrogen oxides, a catalyst carrier for oxidizing organic substances, a photocatalyst, a filter for high temperature, an electronic material and a filler for reinforcement, and the like. It is about the method.

[0002]

2. Description of the Related Art Conventionally, a method for producing titania fiber is as follows: (1) Starting from potassium titanate fiber, the fiber is subjected to depotassium treatment in an acid solution or the like, and then fired to produce titania fiber. (For example, see Japanese Unexamined Patent Publication No.
JP-A-3-41518, JP-A-53-52737, JP-A-55-113625, and JP-B-59-4.
1928, JP-A-1-246139, JP-A-2-164722, etc.), and (2) titania fibers are produced by baking precursor fibers obtained by spinning polytitanoxane as a raw material. (Japanese Unexamined Patent Publication No. 49-124336), (3) a method of concentrating an aqueous titania sol obtained by adding a titanium alkoxide to concentrated hydrochloric acid to obtain a spinning solution, and spinning and firing to obtain titania fibers ( Tokiko 57-2291
No. 3), (4) Titania fiber by so-called sol-gel method, in which hydrolysis and polycondensation are carried out by adding water and hydrochloric acid to an alcohol solution of titanium tetraisopropoxide to form a spinning solution and spin it. (5) a method of preparing a polymer by reacting a titanium alkoxide and an aliphatic dicarboxylic acid in a solvent, and concentrating, spinning and firing to produce titania fiber ( JP-A-60-104133), (6) A method for producing titania fibers by wet spinning an alginic acid solution into continuous fibers, dipping in a titanium solution, drying and firing while stretching. -18
No. 4525) and (7) a method of producing a titania fiber by impregnating an organic fiber with an aqueous solution of titanium alkoxy hydrogen peroxide, followed by firing (Japanese Unexamined Patent Publication (Kokai) No. 2-1956).
No. 9) is known.

However, in the above-mentioned conventional production method, a so-called continuous fiber having an infinite length with respect to the fiber diameter (a fiber having a length of at least several tens cm) is excellent in spinning stability and high. It has been difficult to industrially easily produce titania fiber excellent in mechanical strength.

For example, according to the production method (1), the potassium titanate fiber itself is a so-called short fiber having a fiber length of usually 1 mm or less, and at most about several mm, and it is not possible to produce a continuous fiber. It is possible. In the method of (3), in which the aqueous titania sol is concentrated to obtain titania fibers as a spinning solution, a high-concentration inorganic acid such as concentrated hydrochloric acid is used in the production of the sol. There is a problem that chlorine may remain as impurities in the obtained fiber.

In the method for producing titania fibers by the sol-gel method, hydrolysis and polycondensation of titanium alkoxide proceed in the presence of an acid such as hydrochloric acid to produce a viscous liquid having an appropriate spinning property. This is used as a spinning solution, but it is difficult to control the hydrolysis reaction and the condensation polymerization reaction, and the spinning viscous liquid tends to change into a non-spinning liquid due to aging. There is.

When a polymer is prepared by reacting a titanium alkoxide and an aliphatic dicarboxylic acid in a solvent, an organic group exists between a side chain of the polymer and a titanium atom.
The amount of the organic matter remaining in the polymer is large, and the organic matter content in the precursor fiber is necessarily high. Also, in a method of wet spinning an alginic acid solution and immersing it in a titanium solution, or in a method of impregnating organic fibers with an aqueous solution of titanium alkoxy hydrogen peroxide, the amount of organic substances remaining in the precursor fibers is also large. When such precursor fibers having a large residual amount of organic matter are baked into titania fibers, there is a problem that the mechanical strength of the obtained fibers is low.

The method of (2), in which polytitanoxane is used as a raw material and a precursor fiber obtained by spinning the same is fired to produce titania fiber, requires continuous fiber and requires the use of an organic polymer or a binder. Therefore, it is expected that the mechanical strength of the obtained fiber is high. However, the degree of polymerization of polytitanoxane and the type and residual amount of the organic residue in the side chain affect spinning stability during spinning, and the mechanical strength of the obtained fiber. Preparation of a suitable polytitanoxane is essential, but there is no sufficient disclosure of its preparation method.

[0008] Titanium oxide has also been used as a carrier for reducing nitrogen oxides, as a catalyst carrier for oxidizing organic substances, and as a catalyst carrier for photocatalysts. Depends on the type and amount of the supported catalyst substance, the primary particle size, the aggregated particle size, and the like, and titanium oxide having a large specific surface area and a large pore volume is desired as a support. Further, when used as a catalyst carrier for reducing nitrogen oxides, it is required that the crystal form be an anatase form. Conventionally, the above-mentioned titanium oxide catalyst carrier and photocatalyst are usually used in the form of powder, and as the catalyst for reduction or oxidation, they are used as porous particles or pellets by granulation or molding. .
On the other hand, for silica and alumina, etc., a method of forming these into a fibrous form and applying them as a catalyst carrier has been known for a long time, and a method of increasing the surface area of the fiber for the purpose of improving the performance as a catalyst carrier. As a method, a fiber is immersed in a soluble liquid such as an acid to partially corrode the fiber surface (for example, Japanese Patent Application Laid-Open No. 50-87974 and Japanese Patent Publication No.
No. 11196) is known.

[0009]

Under these circumstances, the inventors of the present invention have an industrial scale and excellent spinning stability.
Titania continuous fiber having high mechanical strength, furthermore, specific surface area, as a result of intensive study to find a titania continuous fiber suitable for a catalyst support having a large pore volume and a production method, titanium alkoxide under specific conditions It is hydrolyzed and polymerized, and the obtained polymer is dissolved in a specific solution, and as a spinning solution, when spinning and firing, a continuous fiber of titania having excellent spinning stability and high mechanical strength can be obtained. In addition, when the precursor fiber is subjected to steam treatment before and / or during firing, the specific surface area is extremely high.
The inventors have found that a catalyst carrier having a large pore volume can be obtained, and have completed the present invention.

[0010]

The first aspect of the present invention is as follows.
A titania fiber having a fiber diameter after firing of 5 to 50 μm, a fiber length of 50 cm or more, and a tensile strength of a single fiber of 0.5 GPa or more by a titanium alkoxide method (meaning a method by hydrolysis and polymerization of titanium alkoxide) is used. To offer.

In the second aspect of the present invention, a hydrolysis reaction and a polymerization reaction are performed by adding water to an alcohol solution of titanium alkoxide to produce a polymer insoluble in the alcohol.
After the precipitation, dissolving the polymer in an organic solvent in which the polymer is soluble to form a spinning solution, and then spinning the spinning solution to obtain a precursor fiber, and then firing the precursor fiber. Another object of the present invention is to provide a method for producing titania fiber.

A third aspect of the present invention is that the fiber diameter is 5 to 50 μm,
Fiber length is 50 cm or more, BET specific surface area is 10 m ² /
g or more, the pore volume measured by the nitrogen adsorption method is 0.05 c
C./g or more, a pore volume having a pore radius of 10 .ANG. or more is 0.02 cc / g or more, and a single fiber has a tensile strength of 0.1 GPa or more. To be.

A fourth aspect of the present invention is that a hydrolysis reaction and a polymerization reaction are performed by adding water to an alcohol solution of titanium alkoxide to produce and precipitate a polymer insoluble in the alcohol. Is re-dissolved in an organic solvent in which the polymer is soluble to form a spinning solution, and then the spinning solution is spun to obtain a precursor fiber, and the obtained precursor fiber is subjected to a steam treatment before and / or during firing. It is another object of the present invention to provide a method for producing the above titania fiber.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The titania fiber of the present invention has a fiber diameter of 5 to 50 μm.
m, the fiber length is 50 cm or more, and the tensile strength of the single fiber is 0.5 GPa or more. When the precursor fiber is subjected to steam treatment before and / or during firing,
Fiber diameter is 5 to 50 μm, fiber length is 50 cm or more, BE
T specific surface area is 10 m ² / g or more, pore volume measured by nitrogen adsorption method is 0.05 cc / g or more, and pore volume having a pore radius of 10 Å or more is 0.02
cc / g or more, and the tensile strength of a single fiber is 0.1 GP
It is a porous titania fiber having physical properties of a or more (hereinafter, may be referred to as a porous titania fiber). BET
When the specific surface area is smaller than 10 m ² / g, the catalyst may be supported on the fiber, or the fiber itself may be used as a catalyst,
It is difficult to obtain sufficient activity.

The porous titania fiber of the present invention has a pore volume measured by a nitrogen adsorption method of 0.05 cc / g or more, preferably 0.10 cc / g or more and a pore radius of 10 Å or more. The volume is 0.02 cc / g or more, preferably 0.04 cc / g or more. When the pore volume is smaller than 0.05 cc / g, sufficient activity may not be obtained even if the fiber is supported with a catalyst or the fiber itself is used as a catalyst.

On the other hand, even when the pore volume having a pore radius of 10 angstroms or more is less than 0.02 cc / g, it is difficult to sufficiently support the catalyst component inside the titania fiber. May not be obtained. Further, the porous titania fiber of the present invention has a tensile strength of a single fiber of 0.1 GPa or more, preferably 0.3 GPa or more. When used in the form of a woven or non-woven fabric, the higher the tensile strength, the better, but this value usually decreases as the pore volume increases. Therefore, it is only necessary to determine which property item has priority depending on the application.

In the method for producing titania fiber of the present invention, the titanium alkoxide used is represented by the general formula [1] T
i (OR ₁ ) ₄ (where R ₁ has ₁ to 4 carbon atoms)
Represents an alkyl group). More specifically, titanium tetramethoxide, titanium tetraethoxide, titanium tetra n-propoxide, titanium tetra iso-propoxide, titanium tetra n-butoxide, titanium tetra s
Examples thereof include ec-butoxide and titanium tetra-tert-butoxide, and among them, titanium tetraiso-propoxide in which R ₁ is an isopropyl group. When the number of carbon atoms of R _{1 in} the general formula [1] exceeds 4, the amount of residual organic matter in the produced polymer increases, and as a result, the mechanical strength of the resulting titania fiber decreases. The alcohol used in the present invention is represented by the general formula [2] R ₂ OH (where R
₂ represents an alkyl group having 1 to 4 carbon atoms), and examples of such alcohols include ethanol and isopropyl alcohol. When the number of carbon atoms of R _{2 in} the general formula [2] exceeds 4, the boiling point becomes high, and it becomes difficult to remove the alcohol in the subsequent step, which is not preferable.

The amount of the alcohol used relative to the titanium alkoxide may be such that the alkoxide and water do not become immiscible during the hydrolysis by adding water, and the alcohol is used in the range of about 0.5 mol to about 50 mol per mol of the titanium alkoxide. Is done. There is no particular problem if the amount is too large, but the cost of separation from the polymer in the subsequent step increases.

In the present invention, only an alcohol solution of titanium alkoxide is used as a raw material solution, and this is hydrolyzed.
The polycondensation reaction causes the obtained polymer to be dissolved in an organic solvent, which is spun as a spinning solution, and the resulting precursor fiber is subjected to steam treatment and then fired to be porous and mechanical. Although high strength titania fiber can be produced, if a titania fiber having higher mechanical strength is desired, the silica content in the titania fiber obtained after firing is about 1 to about 40% by weight. Preferably, a silicon compound is added to the spinning solution.

When the silicon-containing compound is added, the compound may be added to the spinning solution before the spinning solution is spun.
For example, a silicon compound may be mixed in an alcohol solution of a titanium alkoxide, or an alcohol solution of a titanium alkoxide and a compound having active hydrogen, or an organic solvent of a polymer obtained by a hydrolysis / polycondensation reaction. During or after dissolution in the spinning solution, a silicon compound may be added so as to be present in the spinning solution.

The amount of the silicon compound added is such that the silica content in the titania fiber obtained after firing is about 1 to about 40% by weight,
Preferably it will be from about 5 to about 30% by weight. If the silica content exceeds 40% by weight, the mechanical strength of the titania-based fiber obtained no longer increases, but rather the content of titania component is relatively reduced, which causes a decrease in catalytic activity, which is not preferred.

The silicon compound that can be used in the present invention is not particularly limited as long as it can be uniformly mixed and dispersed in titania, but is usually represented by the general formula [3] Si _{n On -1} (OR ₃ )
_The alkyl silicate is preferably represented by _{2n + 2} (wherein, R ₃ represents an alkyl group having 1 to 4 carbon atoms, and n represents a number of 1 or more). Particularly preferred alkyl silicates include ethyl silicates wherein R ₃ in the general formula [3] is an ethyl group and n is 4 to 6.

In the present invention, water is added to an alcohol solution of titanium alkoxide to cause a hydrolysis reaction and a polymerization reaction to form an insoluble polymer in the alcohol solution. In order to control the reaction, a compound having active hydrogen may be added to the alcohol solution. By adding an appropriate amount of the compound having active hydrogen, the hydrolysis reaction and the polymerization reaction of the titanium alkoxide can be controlled, and the solubility of the polymer precipitated in the alcohol in the organic solvent can be improved.

The amount of the compound having active hydrogen is about 0.05 to about 1.9 mol, preferably about 0.1 to about 1.0 mol, per 1 mol of titanium alkoxide. When the amount of the compound having active hydrogen added per mole of titanium alkoxide is less than about 0.05, no addition effect is observed, and when it is more than 1.9, the hydrolysis and polymerization reaction are excessively suppressed. As a result, the polymerization hardly proceeds, the amount of residual organic matter in the obtained polymer increases, and as a result, the mechanical strength of the resulting titania fiber decreases.

The compound having active hydrogen is represented by the general formula [4] R ₄ COCH ₂ COR ₅ (wherein R ₄ and R ₅ represent an alkyl group or an alkoxy group having 1 to 4 carbon atoms). Β-diketone compounds or alkyl salicylates are preferred. More specifically, the use of ethyl acetoacetate and isopropyl acetoacetate as the β-diketone compound, and the use of ethyl salicylate and methyl salicylate as the alkyl salicylate are recommended.

In carrying out the present invention, hydrolysis and polymerization reaction are advanced by adding water to an alcohol solution of titanium alkoxide.
The water is preferably diluted with the same alcohol as the alcohol in which the titanium alkoxide is dissolved to a water concentration of about 1 to about 50% by weight. When water is directly added, the reaction locally proceeds, and a polymer insoluble in an organic solvent may be precipitated.

The temperature for adding water to the alcohol solution of the raw material titanium alkoxide may be any temperature from room temperature or lower to the boiling point of the alcohol used.
There is no particular limitation. However, from an industrial point of view, that is, when a high reaction rate is desired, a higher reaction temperature is preferable. For example, the reaction may be carried out by adding water and alcohol at room temperature and then refluxing at the boiling point.

From the industrial point of view, the higher the titanium concentration, the better. Therefore, the addition of water (alcohol dilution water) to the alcohol solution of titanium alkoxide is performed at the boiling point of the alcohol, and while distilling out the same volume of alcohol as the volume of alcohol contained in the added water, If the addition is performed, a decrease in the titanium concentration due to the addition of water can be suppressed, so this method is industrially recommended.

According to the present invention, water is added to an alcohol solution of titanium alkoxide to cause hydrolysis and polymerization reaction to proceed to form a polymer which is insoluble in the alcohol but soluble in other organic solvents. And deposited. When the hydrolysis and polymerization reaction of the titanium alkoxide according to the present invention is carried out using a solvent other than alcohol, for example, ethers, the resulting polymer tends to have a three-dimensional network structure, and the form in which the solvent is incorporated As a result, the polymer tends to gel, and a polymer having an appropriate degree of polymerization as obtained in the present invention cannot be produced.

In the practice of the present invention, the amount of water to be added to an alcohol solution of titanium alkoxide is important as a condition for forming and depositing a polymer which is insoluble in the alcohol but soluble in other organic solvents. It is. If the amount of water to be added is too small, a polymer soluble in alcohol is obtained. Such a polymer has a low degree of polymerization, and the amount of organic substances remaining in the polymer is relatively high. When spinning is performed using such a polymer and spun, spinning properties are good, but titania fibers with high mechanical strength cannot be obtained because a large amount of organic components remain in the precursor fibers. .

As the amount of water to be added is increased, a polymer insoluble in alcohol is formed and precipitates. If the amount of water to be added is appropriate, it will be insoluble in alcohol but well soluble in other organic solvents. Such a polymer has a high degree of polymerization, has many bonds of titanium-oxygen-titanium, and has a relatively small amount of organic substances. Accordingly, titania fibers obtained by spinning this polymer into a spinning solution have high mechanical strength. However, when the polymerization reaction is promoted by adding a large excess of water, the polymer is not dissolved in not only the alcohol but also other organic solvents, so that the spinning solution cannot be prepared.

The polymer precipitated in the alcohol solution by the hydrolysis / polymerization reaction is then mixed with an organic solvent in a suspended state or after completely or partially removing the alcohol, and dissolved to produce a spinning solution. I do. Usually, it is preferable to completely remove the alcohol from the polymer and dissolve it in an organic solvent. The method of separating the alcohol solution and the polymer is not particularly limited, for example, separation by filtration,
Examples include centrifugation, removal by heat concentration, removal by concentration under reduced pressure, and, if necessary, drying by heating or reduced pressure. Alternatively, the alcohol suspension of the polymer may be partially concentrated, and then an organic solvent in which the polymer is soluble may be added and mixed for dissolution. In this case, it is preferable to remove water in the partially concentrated alcohol suspension. The removal of water in the suspension may be carried out, for example, by adding an alcohol containing no water to the suspension, and removing the water at the same time as removing the alcohol by heating or concentration under reduced pressure.

Water is added to the alcohol solution of titanium alkoxide to form a polymer by hydrolysis and polymerization reaction,
These steps of separating the alcohol solution and the polymer, and further, dissolving the obtained polymer in an organic solvent to produce a spinning solution can be carried out by a batch system or a continuous system.

In the practice of the present invention, the hydrolysis / polymerization reaction of titanium alkoxide is performed by adding water to an alcohol solution of titanium alkoxide and insoluble in the alcohol, but soluble in an organic solvent other than alcohol. What is necessary is just to add water to precipitate a polymer excellent in certain physical properties,
Usually, about 1.5 to about 1 mole of titanium alkoxide is added to water.
It may be added in the range of about 4 mol and subjected to the reaction, but the upper limit of the amount of the water is not necessarily limited, and many experiments have shown that the amount of water added to the alcohol solution of titanium alkoxide is The amount (A) and the step of producing and precipitating a polymer by adding water to the alcohol solution, and separating the precipitated polymer from the alcohol solution until the polymer dissolved in the organic solvent is obtained. The difference (AB) in the amount of discharged water (B) is about 1.5 to about 1.95 mol, preferably about 1.6 to about 1 mol of titanium alkoxide.
The amount of added water may be adjusted so as to be about 1.90 mol. When the amount of water discharged out of the reaction system before obtaining the polymer is large, the amount of added water may be increased. If the difference in the amount of water, that is, the amount of water consumed in the substantial hydrolysis reaction is less than 1.5 mol, the degree of polymerization of the obtained polymer is small,
A polymer having a relatively high organic content is obtained, and even if this is dissolved in an organic solvent and spun as a spinning solution, titania fibers having high mechanical strength cannot be obtained. On the other hand, if the difference in water content exceeds 1.95 mol, it is extremely difficult to dissolve the produced polymer in an organic solvent.

The organic solvent for dissolving the polymer is preferably an organic solvent containing ethers or aromatic hydrocarbons. Since the organic solvent is the main solvent in the spinning solution, a solvent having a high boiling point is not preferred. Preferred organic solvents include tetrahydrofuran, diethyl ether,
Toluene and the like.

The dissolved polymer solution is concentrated by removing the solvent by heating or removing the solvent by reducing the pressure, so that the concentration of the polymer is adjusted to 50 to 80% by weight. In spinning, the viscosity of the spinning solution is controlled.
A suitable spinning solution has a viscosity of about 10 poise to about 2000 poise, preferably about 20 poise to about 500 poise, and these viscosities can be controlled by adjusting the concentration of the spinning solution and the temperature of the spinning solution. it can.

The spinning solution whose viscosity has been adjusted as described above is then spun to obtain a precursor fiber. The spinning method is not particularly limited, and nozzle extrusion spinning, centrifugal spinning,
Known spinning methods such as blow spinning can be applied. In spinning, the precursor fiber can be drawn by a rotating roller or a high-speed air stream. In spinning, adjusting the spinning atmosphere and the temperature and humidity of the blown air is a desirable method for stably obtaining good fibers.

The spun precursor fibers are then subjected to a steam treatment, a hot water treatment, an acid treatment, or a pretreatment of a combination thereof, if necessary, and then fired. The firing method is not particularly limited, and is usually fired in air. If necessary, the titania fibers obtained by firing may be fired again. During firing, the precursor fibers or titania fibers may be fired under tension.

In the firing process, the titania fiber can change from an amorphous fiber to an anatase fiber and a rutile fiber depending on the firing temperature. Further, the crystallization temperature and the transition temperature from anatase to rutile also vary depending on the amount of the silica component contained. Therefore, a desired titania fiber can be obtained by controlling the firing temperature and the silica content. For example, in the case of titania fiber containing no silica component, the firing temperature is about 600 ° C.,
Rutile fibers can be obtained at 00 ° C. In the case of titania fiber containing 15% by weight of a silica component, about 900
The anatase fiber can be obtained by firing at about 1100 ° C., and the rutile fiber can be obtained by firing at about 1100 ° C. By the above method, titania continuous fibers having a fired fiber diameter of 5 to 50 μm, a fiber length of 50 cm or more, and a single fiber tensile strength of 0.5 GPa or more can be obtained.

The fiber diameter is 5 to 50 μm, the fiber length is 50 cm or more, the BET specific surface area is 10 m ² / g or more, and the pore volume measured by the nitrogen adsorption method is 0.05 cc / g or more. In order to obtain a titania fiber having a pore volume having a pore radius of not less than Angstroms and a physical property of not less than 0.02 cc / g and a tensile strength of a single fiber of not less than 0.1 GPa, the production method described above The precursor fiber obtained by spinning before firing is heated to about 80 ° C. to about 300 ° C.
° C, under an atmosphere having a water vapor partial pressure of about 0.3 atm or more,
After the steam treatment under the condition of 0.5 hour or more, usually about 1 hour to about 24 hours, firing may be performed. The higher the temperature and the partial pressure of steam during the steam treatment, the shorter the treatment time. When the treatment temperature is lower than 80 ° C., a long treatment is required even if the steam partial pressure is high, which is not industrially preferable. Also, when the partial pressure of water vapor is low, a long-time treatment is required. In the present invention, the steam treatment of the precursor fiber is usually performed before firing. However, if the above-mentioned temperature conditions, steam partial pressure, and processing time can be satisfied, steam treatment can be incorporated in the firing step.

In the method of the present invention, it is not clear why the porous titanium dioxide fiber having a large pore volume is obtained by the steam treatment, but the precursor fiber obtained by spinning from the above-mentioned spinning solution is not described. Contains a solvent and an organic component based on the organic group of the polymer side chain, and when the precursor fiber is subjected to steam treatment, the polymer in the fiber is further hydrolyzed, and the organic component of the side chain is Is considered to be removed to change to an OH group, and the Ti—O—Ti bond is increased by the polymerization reaction. Desorption of this organic component and Ti
Due to the formation of -O-Ti bonds, many voids are formed in the fiber, and since the size of the voids is relatively large, even in the firing process, the voids remain without disappearing. It seems to be fiber. In the firing process, the organic components in the precursor fibers are almost completely eliminated by 300 ° C. Therefore, steam treatment is about 300
C., preferably at a temperature of 200.degree.

The method of firing the precursor fiber after the steam treatment is not particularly limited, and is usually fired in air. If necessary, the titania fibers obtained by firing may be fired again. During firing, the precursor fibers or titania fibers may be fired under tension. The firing temperature for producing the porous titania fiber is not particularly limited, but is usually in the range of about 500C to about 1100C. The higher the firing temperature, the lower the porosity, that is, the BET specific surface area and the pore volume, but the higher the firing temperature, the higher the firing temperature and the higher the firing temperature under a high steam partial pressure atmosphere. However, porosity is maintained. When the sintering temperature is lower than 500 ° C., the fiber is a porous fiber, but when the fiber strength is lower than 1100 ° C., the porosity decreases.

The porous titania fiber thus obtained exhibits particularly excellent properties as a catalyst or a catalyst carrier. The continuous titania fiber obtained by the present invention is used in various applications in the form of a long fiber or in the form of a short fiber obtained by cutting the fiber.

[0044]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. The water concentration in alcohol, fiber diameter,
Tensile strength, fiber crystal form, BET specific surface area, and pore volume were measured by the following methods.

Moisture concentration in alcohol: A sample was measured with a Karl Fischer moisture meter (MKS-21, manufactured by Kyoto Electronics Co., Ltd.).
Using 0), the water concentration was measured.

Fiber diameter: The sample was observed with an optical microscope, 20 fibers present in the visual field were randomly selected, the fiber diameter was measured, and the average value was calculated to obtain the fiber diameter.

Tensile strength: A single fiber automatic tensile tester (manufactured by Toyo Baldwin Co., Ltd., control unit; model AM)
FC, tension device part; TENSILON, UTM-2-
Using 20), the fiber was pulled at a measurement length of 25 mm and a tensile speed of 1 mm / min, and the strength at which the fiber broke was defined as the tensile strength. The measured value is the average value of the tensile strength of 30 single fibers.

Crystal form of fiber: The fiber is crushed lightly in a mortar and X-ray diffractometer (RAD-II, manufactured by Rigaku Corporation)
Analyzed using A).

BET specific surface area of the fiber: The fiber is lightly ground in a mortar, and is subjected to Micrometrics Flowsorb II 23.
00 (manufactured by Shimadzu Corporation).

Fiber pore volume: The fiber is crushed lightly in a mortar, and a gas adsorption / desorption analyzer Omnisorp 360 is used.
(Manufactured by COULTER) using nitrogen gas.

Example 1 Titanium isopropoxide (Wako Pure Chemicals, first grade reagent) 30
0.0 g, and 54.9 g of ethyl acetoacetate (Wako Pure Chemicals, special grade of reagent) were added to isopropyl alcohol (Wako Pure Chemicals,
Dissolved in 700.0 g of a reagent
The mixture was refluxed for a time to prepare an alcohol solution of the raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.40. 51.0 g of pure water
Was mixed with 460.2 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 10% by weight. This water content is 2.7 moles per mole of titanium alkoxide. The alcohol solution as a raw material was heated in a nitrogen atmosphere and refluxed under boiling. At the same time, an alcohol solution having a water concentration of 10% by weight was added with stirring while distilling off the alcohol. The distillation rate of the alcohol and the addition rate were adjusted to be substantially equal, and the addition time was adjusted to be 135 minutes. From the start of the addition, when about 2.1 mol of water was added to 1 mol of the titanium alkoxide, the precipitation of the polymer started, and when the entire amount of water was added, a complete slurry was obtained. When the water in the distilled alcohol was analyzed, the amount of water was 0.29 mol per 1 mol of titanium alkoxide. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and heating was continued in an oil bath at 143 ° C. until no distillate was produced, to dry the polymer. The polymer after drying was a yellow powder, and the weight was 144 g. The amount of water discharged out of the system by this operation was 0.61 mol per 1 mol of titanium alkoxide.
Therefore, the difference between the amount of water added and the amount of water discharged out of the system together with the alcohol or the like [2.7− (0.29 + 0.
61)] corresponds to 1 mol of titanium alkoxide.
The amount was 80 moles. After dissolving the polymer in 460 g of tetrahydrofuran (Wako Pure Chemical Industries, special grade of reagent), 37.2 g of ethyl silicate 40 (Tama Chemical Industry) was added and refluxed for 1 hour. The amount of ethyl silicate added is such that the titania-based fiber obtained by spinning and firing becomes 15% by weight as silica. After filtering the polymer solution with a 3 μm membrane filter made of Teflon,
The mixture was heated to distill off tetrahydrofuran and concentrated.
0 g of spinning solution was obtained. At this time, the viscosity of the spinning solution is 40 ° C.
Was 50 poise. 20 kg of the spinning solution at 40 ° C.
/ Cm ² of nitrogen gas through a nozzle with a diameter of 50 μm.
Extruded into an air atmosphere of 0 ° C. and 60% RH, 70 m /
The precursor fiber was wound at a speed of minutes. The obtained precursor fiber was placed in a constant temperature / humidity chamber at 70 ° C. and 70% RH and subjected to a steam treatment for 30 minutes, and then the temperature was raised at a rate of 200 ° C./h.
r, baking in air at 900 ° C. for 30 minutes to obtain titania fiber. The obtained titania fiber has a fiber diameter of 15 μm.
And the tensile strength was as high as 1.4 GPa. According to XRD analysis, the fiber was anatase-type titanium oxide, and no peak other than anatase was observed.

Example 2 The steam-treated precursor fiber obtained in Example 1 was fired in air at 1100 ° C. for 30 minutes. The obtained titania fiber had a fiber diameter of 15 μm and a high tensile strength of 1.1 GPa. Also, XRD
According to analysis, the fiber is rutile titanium oxide,
No peak other than rutile was observed.

Example 3 300.0 g of titanium isopropoxide and 54.9 g of ethyl acetoacetate were added to 128.
6 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. 51.0 g of pure water
Was mixed with 1653.3 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 3% by weight. The alcohol solution as a raw material was heated in a nitrogen atmosphere and refluxed under boiling. At the same time, an alcohol solution having a water concentration of 3% by weight was added with stirring while distilling off the alcohol. The distillation rate of the alcohol and the addition rate were adjusted to be substantially equal, and the addition time was 140 minutes. At the time when all the water was added, the slurry was completely in a slurry state. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and the heating was continued in a 143 ° C. oil bath until no distillate was produced, to dry the polymer. When the amount of water discharged out of the system was measured in the same manner as in Example 1, the difference between the amount of water added and the amount of water discharged out of the system was 1.78 mol. After dissolving the polymer in 460 g of tetrahydrofuran, 3 parts of ethyl silicate 40 were added.
7.2 g was added and refluxed for 1 hour.
Preparation, spinning, and baking as a spinning solution were performed in the same manner as in the above to obtain titania fibers. When the physical properties of the fiber thus obtained were measured, the crystal form of the fiber was anatase-type titanium oxide, the fiber diameter was 16 μm, and the tensile strength was 1.2 GPa.
Met.

Example 4 A polymer slurry was prepared in the same manner as in Example 1, except that the method of preparing the alcohol solution as the raw material and the method of adding the alcohol solution having a water concentration of 10% by weight were used. The slurry was concentrated using an oil bath at 80 ° C. and an evaporator, and further dried under vacuum to obtain a polymer powder. After dissolving the polymer in 270 g of tetrahydrofuran, 37.2 g of ethyl silicate 40 was added and refluxed for 1 hour. A spinning solution was prepared as in Example 1, spun and fired to obtain titania fibers. . The difference between the amount of water added in the present method and the amount of water discharged out of the system was 1.72 mol, and the crystal form of the obtained fiber was anatase type titanium oxide;
The fiber diameter was 16 μm, and the tensile strength was 1.3 GPa.

Example 5 300.0 g of titanium isopropoxide and 54.9 g of ethyl acetoacetate were added to 73.6 of isopropyl alcohol.
g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. 34.2 g of pure water
Was mixed with 79.8 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 30% by weight. This water content is 1.8 moles per mole of titanium alkoxide. The alcohol solution of the raw material is cooled to 10 ° C. in a nitrogen atmosphere, and the alcohol solution having a water concentration of 30% by weight is stirred.
Was added. The addition time was 45 minutes. At the time when the total amount of water was added, the solution was still a transparent solution, but the precipitation of the polymer was started by heating and the slurry was completely in a slurry state at the reflux temperature. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and heating was continued in a 120 ° C. oil bath until no distillate was produced, thereby drying the polymer. After dissolving the polymer in 270 g of tetrahydrofuran, 37.2 g of ethyl silicate 40 was added and refluxed for 1 hour,
A spinning solution was prepared in the same manner as in Example 1, and this was spun and fired in the same manner as in Example 1 to obtain titania fibers. The difference between the amount of water added in this method and the amount of water discharged out of the system was 1.69 mol, the crystal form of the obtained fiber was anatase type titanium oxide, the fiber diameter was 15 μm, and the tensile The strength was 0.9 GPa.

Example 6 300.0 g of titanium isopropoxide and 68.7 g of ethyl acetoacetate were added to isopropyl alcohol 700.
0 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.50. 56.4 g of pure water was mixed with 1837.8 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 3% by weight. This water content is 3.0 moles per mole of titanium alkoxide. The raw material alcohol solution is heated in a nitrogen atmosphere and refluxed under boiling. At the same time, while distilling off the alcohol, the water concentration is 3% by weight.
Was added with stirring. The distillation rate of the alcohol and the addition rate were adjusted to be substantially equal, and the addition time was 160 minutes. At the time when all the water was added, the slurry was completely in a slurry state. Add the slurry to 1
After reflux for an hour, the alcohol was distilled off by heating as it was to obtain 305 g of a concentrated slurry. After adding 460 g of tetrahydrofuran to the concentrated slurry to dissolve it, 37.2 g of ethyl silicate 40 was added thereto, and 1
The mixture was refluxed for a time, a spinning solution was prepared in the same manner as in Example 1, and this was spun and fired in the same manner as in Example 1 to obtain titania fibers. The difference between the amount of water added in this method and the amount of water discharged out of the system was 1.84 mol, the crystal form of the obtained fiber was anatase type titanium oxide, and the fiber diameter was 1
6 μm, and the tensile strength was 1.1 GPa.

Example 7 Titanium isopropoxide (300.0 g) and ethyl acetoacetate (54.9 g) were added to isopropyl alcohol 700.
0 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. 37.2 g of ethyl silicate 40 was added to the alcohol solution, and reflux was further performed for 1 hour. An alcohol solution containing 51.0 g of pure water and 460.2 g of isopropyl alcohol having a water concentration of 10% by weight was added in the same manner as in Example 1 while distilling off the alcohol under heating and boiling. At the time when all the water was added, the slurry was completely in a slurry state. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and the heating was continued in a 143 ° C. oil bath until no distillate was produced, to dry the polymer. The polymer was treated with tetrahydrofuran 270
g of ethyl silicate 40, and
In addition, the mixture was refluxed for 1 hour, a spinning solution was prepared in the same manner as in Example 1, and this was spun and fired in the same manner as in Example 1 to obtain titania fibers. The difference between the amount of water added in this method and the amount of water discharged out of the system was 1.83 mol, the crystal form of the obtained fiber was anatase type titanium oxide, the fiber diameter was 15 μm, The strength was 0.9 GPa.

Example 8 300.0 g of titanium isopropoxide and 13.7 g of ethyl acetoacetate were added to 700.
0 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.10. 46.9 g of pure water was mixed with 1530.5 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 3% by weight. This water content is 2.5 moles per mole of titanium alkoxide. While distilling the alcohol under heating and boiling, an alcohol solution having a water concentration of 3% by weight was added. At the time when all the water was added, the slurry was completely in a slurry state. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and the heating was continued in a 143 ° C. oil bath until no distillate was produced, to dry the polymer. After dissolving the polymer in 460 g of tetrahydrofuran, 37.2 g of ethyl silicate 40 was added and refluxed for 1 hour. Then, preparation, spinning and baking as a spinning solution were performed in the same manner as in Example 1 to obtain titania fibers. . The difference between the amount of water added in this method and the amount of water discharged out of the system is 1.6.
7 mol amount, the crystal form of the obtained fiber is anatase type titanium oxide, the fiber diameter is 16 μm, and the tensile strength is 1.0 G
Pa.

Example 9 Titanium isopropoxide (300.0 g) and ethyl acetoacetate (24.7 g) were added to isopropyl alcohol 700.
0 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.18. 46.9 g of pure water was mixed with 1530.5 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 3% by weight. This water content is 2.5 moles per mole of titanium alkoxide. While distilling the alcohol under heating and boiling, an alcohol solution having a water concentration of 3% by weight was added. At the time when all the water was added, the slurry was completely in a slurry state. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and the heating was continued in a 143 ° C. oil bath until no distillate was produced, to dry the polymer. After heating and dissolving the polymer in 460 g of tetrahydrofuran, the solution was filtered through a 3 μm membrane filter made of Teflon,
The mixture was heated to distill off tetrahydrofuran and concentrated to obtain a spinning solution. Using this spinning solution, titania fibers were obtained in the same manner as in Example 1 except that the firing temperature was set at 600 ° C. The difference between the amount of water added in this method and the amount of water discharged out of the system was 1.69 mol, the crystal form of the obtained fiber was anatase type titanium oxide, and the fiber diameter was 17 μm.
m, and the tensile strength was 0.8 GPa.

Example 10 The firing conditions in Example 9 were changed to 600 ° C. 9 more than 30 minutes
A titania fiber was obtained in the same manner except that the temperature was changed to 00 ° C. for 30 minutes. The crystal form of the fiber obtained by this method was rutile titanium oxide, the fiber diameter was 17 μm, and the tensile strength was 0.7 GPa.

Example 11 In Example 8, the amount of ethyl acetoacetate was 34.3 g (the molar ratio of ethyl acetoacetate to titanium isopropoxide was 0.25), and the amount of ethyl silicate 40 added was 90.4 g ( The titania fiber was obtained in the same manner except that the addition amount of ethyl silicate was 30% by weight as silica in the titania-based fiber obtained by spinning and firing. The difference between the amount of water added in this method and the amount of water discharged out of the system was 1.68 mol, the crystal form of the obtained fiber was anatase type titanium oxide, the fiber diameter was 15 μm, and the tensile The strength was 0.9 GPa.

Example 12 In Example 8, 137.3 g of ethyl acetoacetate was used.
(The molar ratio of ethyl acetoacetate to titanium isopropoxide was 1.00), and a titania fiber was obtained in the same manner. The difference between the amount of water added in the present method and the amount of water discharged out of the system was 1.76 mol,
The crystal form of the obtained fiber was anatase type titanium oxide, the fiber diameter was 15 μm, and the tensile strength was 0.8 GPa.

Example 13 Titanium isopropoxide (200.0 g) was dissolved in isopropyl alcohol (371.4 g) to prepare a raw material alcohol solution. 33.8 g of pure water was mixed with 1103.0 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 3% by weight. This water content is 2.7 moles per mole of titanium alkoxide. While distilling the alcohol under heating and boiling, an alcohol solution having a water concentration of 3% by weight was added. At the time when all the water was added, the slurry was completely in a slurry state. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and the heating was continued in a 130 ° C. oil bath until no distillate was produced, to dry the polymer. After dissolving the polymer in 270 g of tetrahydrofuran, 37.2 g of ethyl silicate 40 was added and refluxed for 1 hour. A spinning solution was prepared in the same manner as in Example 1, and this was spun and fired in the same manner as in Example 1. Thus, titania fibers were obtained. The difference between the amount of water added in this method and the amount of water discharged out of the system is 1.
68 mol amount, the crystal form of the obtained fiber is anatase type titanium oxide, the fiber diameter is 16 μm, and the tensile strength is 1.0.
GPa.

Example 14 200.0 g of titanium isopropoxide and 46.7 g of ethyl salicylate (Wako Pure Chemicals, special grade of reagent) were dissolved in 324.7 g of isopropyl alcohol, and refluxed under a nitrogen atmosphere for 1 hour to obtain a raw material. Was prepared. At this time, the molar ratio of ethyl salicylate to titanium isopropoxide is 0.40. Pure water 3
1.5 g was mixed with 284.3 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 10% by weight. This water content is 2.5 moles per mole of titanium alkoxide.
It is a molar amount. While distilling off the alcohol under heating and boiling, an alcohol solution having a water concentration of 10% by weight was added. At the time when all the water was added, the slurry was completely in a slurry state. After the slurry was refluxed for 1 hour, the alcohol was distilled off by heating as it was.
The heating was continued until no distillate was produced in the oil bath of No. 1 to dry the polymer. The polymer was treated with tetrahydrofuran 27
After dissolving in 0 g, ethyl silicate 40 was added to 37.2.
g and refluxed for 1 hour to prepare a spinning solution in the same manner as in Example 1. The spinning solution was spun and fired in the same manner as in Example 1 to obtain titania fibers. The difference between the amount of water added in this method and the amount of water discharged out of the system was 1.75 mol, the crystal form of the obtained fiber was anatase type titanium oxide, the fiber diameter was 14 μm, and the tensile The strength was 0.9 GPa.

Example 15 300.0 g of titanium isopropoxide and 54.9 g of ethyl acetoacetate were added to 73.6 of isopropyl alcohol.
g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.40. 43.6 g of pure water was mixed with 393.2 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 10% by weight. This water content is 2.3 moles per mole of titanium alkoxide. The alcohol solution as a raw material was heated in a nitrogen atmosphere and refluxed under boiling. At the same time, an alcohol solution having a water concentration of 10% by weight was added with stirring while distilling off the alcohol. The distillation rate of the alcohol and the addition rate were adjusted to be substantially equal, and the addition time was adjusted to be 160 minutes. At the time when all the water was added, the slurry was completely in a slurry state.
The amount of water discharged out of the system by this operation was 0.20 mol per 1 mol of titanium alkoxide. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was to obtain 305 g of a concentrated slurry. The amount of water discharged out of the system by this operation was 0.17 mol per 1 mol of titanium alkoxide. The concentrated slurry was heated to allow the alcohol to flow out, and at the same time, 700 g of isopropyl alcohol was added to dehydrate the slurry. The distillation rate and the addition rate were equal, and the addition time was 1.5 hours. The amount of water discharged out of the system by this operation was 0.24 mol per 1 mol of titanium alkoxide. Therefore, the difference between the amount of water added and the amount of water discharged out of the system together with alcohol or the like [2.3- (0.20 + 0.17 + 0.24)]
Was 1.69 mol with respect to 1 mol of titanium alkoxide. 352 g of tetrahydrofuran was added to and dissolved in the dehydrated concentrated slurry. Then, 37.2 g of ethyl silicate 40 was added, and the mixture was refluxed for 1 hour to prepare a spinning solution in the same manner as in Example 1. Spinning and firing were performed in the same manner as in the above to obtain titania fibers. The crystal form of the obtained fiber is anatase type titanium oxide, and the fiber diameter is 1
5 μm, and the tensile strength was 1.1 GPa.

Example 16 When spinning the spinning solution obtained in Example 15, the diameter was 30 μm.
A titania fiber was obtained by spinning and firing in the same manner as in Example 1 except that a nozzle of m was used. The crystal form of the obtained fiber was anatase type titanium oxide, the fiber diameter was 10 μm, and the tensile strength was 1.3 GPa.

Comparative Example 1 Titanium isopropoxide (300.0 g) and ethyl acetoacetate (41.2 g) were added to isopropyl alcohol 700.
0 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.30. 24.3 g of pure water was mixed with 793.1 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 3% by weight. This water content is 1.3 moles per mole of titanium alkoxide. While distilling the alcohol under heating and boiling, an alcohol solution having a water concentration of 3% by weight was added. Even when the entire amount of water was added, no precipitation of the polymer was observed, and the solution was a transparent solution. The clear solution was heated and concentrated, and alcohol was removed. However, no polymer was observed, and the solution remained a liquid.It was not a viscous liquid having spinnability and could not be used as a spinning solution. Met. In this comparative example, the difference between the amount of water added and the amount of water discharged outside the system was 1.22 mol.

Comparative Example 2 Titanium isopropoxide (300.0 g) and ethyl acetoacetate (54.9 g) were added to isopropyl alcohol 700.
0 g, and refluxed for 1 hour under a nitrogen atmosphere to prepare an alcohol solution of a raw material. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.40. 113.6 g of pure water was mixed with 1024.6 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 10% by weight. This water content is 6.0 moles per mole of titanium alkoxide. While distilling off the alcohol under heating and boiling, an alcohol solution having a water concentration of 10% by weight was added. At the time when all the water was added, the slurry was completely in a slurry state. As a result of analyzing the water in the distilled alcohol, 1.83 mol of water was discharged out of the system with respect to 1 mol of titanium alkoxide. After refluxing the slurry for 1 hour, the alcohol was distilled off by heating as it was, and the heating was continued in a 130 ° C. oil bath until no distillate was produced, to dry the polymer. The amount of water discharged out of the system by this operation was 2.12 mol per 1 mol of titanium alkoxide. Therefore, the difference between the amount of water added and the amount of water discharged out of the system was 2.05 mol per 1 mol of titanium alkoxide. 460 g of tetrahydrofuran was added to the polymer and heated, but the polymer hardly dissolved. Therefore, it was impossible to prepare a spinning solution.

Comparative Example 3 100.0 g of titanium isopropoxide and 11.4 g of ethyl acetoacetate were added to 233.3 g of tetrahydrofuran.
And reflux for 1 hour under nitrogen atmosphere.
A raw material tetrahydrofuran solution was prepared. At this time,
The molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.25. 10.7 g of pure water was mixed with 1781.7 g of tetrahydrofuran to prepare a tetrahydrofuran solution having a water concentration of 0.6% by weight. This water content is 1.7 moles per mole of titanium alkoxide.
While distilling under heating boiling, a tetrahydrofuran solution having a water concentration of 0.6% by weight was added. Even when the entire amount of water was added, no precipitation of the polymer was observed, and the solution was a transparent solution.
To this solution, 12.4 g of ethyl silicate 40 was added, refluxed for 1 hour, and then concentrated by heating to obtain a viscous liquid having spinnability. The viscosity at this time was 50 poise at 40 ° C. Spinning was performed in the same manner as in Example 1, and titania fibers were obtained by steaming and firing. In this comparative example, the difference between the amount of water added and the amount of water discharged out of the system was 1.68 mol, the crystal form of the obtained fiber was anatase type titanium oxide, and the fiber diameter was 16 μm. The tensile strength was 0.4 GPa.

Comparative Example 4 Titanium isopropoxide (100.0 g) and ethyl acetoacetate (11.4 g) were added to tetrahydrofuran (233.3 g).
And reflux for 1 hour under nitrogen atmosphere.
A raw material tetrahydrofuran solution was prepared. At this time,
The molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.25. Pure water (11.3 g) was mixed with tetrahydrofuran (1886.6 g) to prepare a tetrahydrofuran solution having a water concentration of 0.6% by weight. This water content is 1.8 moles per mole of titanium alkoxide.
While distilling under heating boiling, a tetrahydrofuran solution having a water concentration of 0.6% by weight was added. Even when the entire amount of water was added, no precipitation of the polymer was observed, and the solution was a transparent solution.
When this transparent liquid was refluxed for 1 hour, the entire liquid finally solidified into an agar-like state due to local gelation, making it impossible to prepare a spinning liquid.

Example 17 A precursor fiber obtained by spinning from the spinning solution of Example 15 in the same manner as in Example 1 was subjected to constant temperature and constant humidity of 85 ° C. and a relative humidity of 95% (water vapor partial pressure of 0.54 atm). After being placed in a vessel and subjected to a steam treatment for 15 hours, it was baked at 900 ° C. for 30 minutes in the air at a heating rate of 200 ° C./hr to obtain titania fibers. The obtained titania fiber has a fiber diameter of 16 μm, BE
The T specific surface area is 132 m ² / g, the pore volume by the nitrogen adsorption method is 0.22 cc / g, and the pore volume having a pore radius of 10 Å or more is 0.22 cc / g.
g. The tensile strength is 0.2 GPa, and X
According to RD analysis, the fiber was titanium oxide in anatase form, and no peak other than anatase was observed.

Example 18 A precursor fiber obtained by spinning from the spinning solution of Example 15 in the same manner as in Example 1 was subjected to a constant temperature and constant humidity of 85 ° C. and a relative humidity of 95% (water vapor partial pressure of 0.54 atm). After being placed in a vessel and subjected to a steam treatment for 5 hours, it was baked at 700 ° C. for 30 minutes in air at a heating rate of 200 ° C./hr to obtain titania fibers. The obtained titania fiber has a fiber diameter of 16 μm, BE
The T specific surface area is 153 m ² / g, the pore volume by the nitrogen adsorption method is 0.14 cc / g, and the pore volume having a pore radius of 10 Å or more is 0.06 cc.
/ G. The tensile strength is 0.6 GPa,
According to XRD analysis, the fiber was anatase form of titanium oxide.

Example 19 The precursor fiber obtained in Example 1 was used at 95 ° C. and a relative humidity of 9
After being placed in a 5% (steam pressure: 0.79 atm) constant temperature / humidity chamber and subjected to steam treatment for 24 hours, the heating rate was increased to 20%.
It was baked at 500C for 30 minutes in air at 0 ° C / hr to obtain titania fibers. The obtained titania fiber had a fiber diameter of 17 μm, a BET specific surface area of 219 m ² / g, a pore volume by a nitrogen adsorption method of 0.35 cc / g, and 1
The pore volume having a pore radius of 0 Å or more was 0.24 cc / g. The tensile strength is 0.1G
Pa, and according to XRD analysis, the fiber was anatase-type titanium oxide.

Example 20 The precursor fiber obtained in Example 1 was used at 95 ° C. and a relative humidity of 9
After being placed in a 5% (steam pressure: 0.79 atm) constant temperature / humidity chamber and subjected to steam treatment for 24 hours, the heating rate was increased to 20%.
It was baked at 900C for 30 minutes in air at 0C / hr to obtain titania fibers. The obtained titania fiber had a fiber diameter of 17 μm, a BET specific surface area of 104 m ² / g, a pore volume of 0.21 cc / g by a nitrogen adsorption method, and
The pore volume having a pore radius of 0 Å or more was 0.21 cc / g. The tensile strength is 0.2G
Pa, and according to XRD analysis, the fiber was anatase-type titanium oxide.

Example 21 A precursor fiber obtained by spinning the spinning solution of Example 15 in the same manner as in Example 1 was fired in a tubular furnace. At this time, when the furnace temperature reached 100 ° C., moist air having a partial pressure of steam of 0.38 atm was sent into the tubular furnace by bubbling air into water at 75 ° C.
Hold at 0 ° C. for 2 hours, then switch to dry air,
It was baked at 00 ° C. for 30 minutes to obtain titania fibers. The obtained titania fiber has a fiber diameter of 16 μm, a BET specific surface area of 66 m ² / g, a pore volume by a nitrogen adsorption method of 0.12 cc / g, and a pore having a pore radius of 10 Å or more. The volume was 0.06 cc / g. Further, the tensile strength was 0.7 GPa, and the fiber was anatase-type titanium oxide according to XRD analysis.

Comparative Example 5 The precursor fiber obtained in Example 1 was heated at 900 ° C. in air at a rate of 200 ° C./hr without steam treatment.
After baking for 0 minutes, a titania fiber was obtained. The obtained titania fiber was black due to residual carbon, was very brittle, and had a tensile strength of less than 0.1 GPa. B
The ET specific surface area was 6 m ² / g.

Comparative Example 6 The precursor fiber obtained in Example 1 was treated at 70 ° C. and a relative humidity of 7
After a steam treatment for 1 hour in a thermo-hygrostat of 0% (steam partial pressure 0.22 atm), the temperature was raised at a rate of 200.
Calcination was performed at 900 ° C for 30 minutes in the air at 900C / hr to obtain titania fibers. The obtained titania fiber had a BET specific surface area of 0.2 m ² / g and a pore volume by a nitrogen adsorption method of 0.01 cc / g. The tensile strength of the fiber was 1.2 GPa.

[0078]

As described in detail above, according to the present invention, continuous fibers of titania having excellent spinning stability and high mechanical strength can be industrially easily produced. When the precursor fiber obtained by the method is subjected to steam treatment under specific conditions before or during the firing process, it is possible to obtain a titania continuous fiber having an excellent specific surface area and a large pore volume as a catalyst or a catalyst carrier. The industrial value is very large.

Claims (21)

[Claims] 1. A fiber having a fiber diameter of 5 to 50 μm and a fiber length of 50
cm. and a titania fiber obtained by a titanium alkoxide method and having a tensile strength of a single fiber of 0.5 GPa or more. 2. A method in which water is added to an alcohol solution of titanium alkoxide to carry out a hydrolysis reaction and a polymerization reaction to generate and precipitate a polymer insoluble in the alcohol. A method for producing titania fiber, comprising: dissolving in a soluble organic solvent to form a spinning solution; spinning the spinning solution to obtain a precursor fiber; and firing the precursor fiber. 3. The spinning solution according to claim 2, wherein at least before spinning, the silicon compound is present in the spinning solution such that the silica content in the titania fiber obtained after firing is 40% by weight or less. A method for producing titania fiber. 4. The method according to claim 1, wherein the alcohol solution of titanium alkoxide to be subjected to the hydrolysis / polymerization reaction contains a compound having an active hydrogen in an amount of 0.05 to 1.9 mol per 1 mol of titanium alkoxide. Item 2. The method for producing titania fiber according to Item 2. 5. An alcohol solution of titanium alkoxide which undergoes a hydrolysis / polymerization reaction contains 0.05 to 1.9 moles of a β-diketone compound or an alkyl salicylate per mole of titanium alkoxide. The method for producing a titania-based fiber according to claim 2. 6. An alcohol solution of titanium alkoxide is subjected to hydrolysis / polymerization reaction by adding water to produce and precipitate a polymer insoluble in the alcohol, and then the alcohol solution is dissolved in the alcohol solution from the alcohol solution. 3. The method for producing titania fiber according to claim 2, wherein the polymer is separated, and the separated polymer is dissolved in an organic solvent in which the polymer is soluble to form a spinning solution. 7. The method for producing titania fiber according to claim 2, wherein the amount of water to be added is 1.5 to 4.0 mol per 1 mol of titanium alkoxide. 8. The difference between the amount of water added to the alcohol solution of titanium alkoxide and the amount of water discharged out of the system before the step of dissolving the polymer obtained by the hydrolysis / polymerization reaction in the organic solvent is as follows: 3. The method for producing titania fiber according to claim 2, wherein a hydrolysis and polymerization reaction is carried out in an amount of 1.5 to 1.95 mol per 1 mol of titanium alkoxide to obtain a polymer. 9. The method for producing titania fiber according to claim 2, wherein the organic solvent in which the polymer is dissolved is an organic solvent containing ethers or aromatic hydrocarbons. 10. The method for producing titania fiber according to claim 3, wherein the silicon compound is an alkyl silicate. 11. A fiber having a fiber diameter of 5 to 50 μm and a fiber length of 5
0 cm or more, the BET specific surface area is 10 m ² / g or more, the pore volume measured by the nitrogen adsorption method is 0.05 cc / g or more, and the pore volume having a pore radius of 10 Å or more is 0.02 cc / g. g, and the tensile strength of the single fiber is 0.1 GPa or more. 12. After adding water to an alcohol solution of titanium alkoxide to carry out a hydrolysis reaction and a polymerization reaction to generate and precipitate a polymer insoluble in the alcohol, the polymer is converted into a polymer. A spinning solution obtained by re-dissolving the precursor solution in a soluble organic solvent, spinning the spinning solution to obtain a precursor fiber, and subjecting the obtained precursor fiber to steam treatment before and / or during firing. Item 14. A method for producing titania fiber having fiber properties according to item 11. 13. The steam treatment condition of the precursor fiber is maintained at a temperature of 85 ° C. to 300 ° C. in an atmosphere having a steam partial pressure of 0.3 atm or more for 0.5 hours or more. A method for producing the titania fiber according to the above. 14. The spinning solution according to claim 12, wherein the silicon compound is present in the spinning solution at least before spinning so that the silica content in the titania fiber obtained after firing is 40% by weight or less. A method for producing titania fiber. 15. An alcohol solution of titanium alkoxide which undergoes a hydrolysis / polymerization reaction contains a compound having active hydrogen in an amount of 0.05 to 1.9 mol based on 1 mol of titanium alkoxide. Item 13. The method for producing titania fiber according to Item 12. 16. An alcohol solution of titanium alkoxide which undergoes a hydrolysis / polymerization reaction contains 0.05 to 1.9 moles of a β-diketone compound or an alkyl salicylate per mole of titanium alkoxide. The method for producing a titania-based fiber according to claim 12, wherein 17. An alcohol solution of titanium alkoxide is subjected to hydrolysis and polymerization by adding water to produce and precipitate a polymer insoluble in the alcohol. 13. The method for producing titania fiber according to claim 12, wherein the polymer is separated, and the separated polymer is dissolved in an organic solvent in which the polymer is soluble to form a spinning solution. 18. The method for producing titania fiber according to claim 12, wherein the amount of water to be added is 1.5 to 4.0 mol per 1 mol of titanium alkoxide. 19. The difference between the amount of water added to the alcohol solution of titanium alkoxide and the amount of water discharged out of the system before the step of dissolving the polymer obtained by the hydrolysis / polymerization reaction in the organic solvent is as follows: The method for producing a titania fiber according to claim 12, wherein the hydrolysis and polymerization reaction is carried out in an amount of 1.5 to 1.95 mol per 1 mol of the titanium alkoxide to obtain a polymer. 20. The method for producing titania fiber according to claim 12, wherein the organic solvent in which the polymer is dissolved is an organic solvent containing ethers or aromatic hydrocarbons. 21. The method for producing titania fiber according to claim 14, wherein the silicon compound is an alkyl silicate.